Are You Training Your Core Slings? (Part 2)

As I discussed in my previous post, the body acts as a yin and yang to produce all sorts of movements. Forces are transmitted from one side of the body to the other, allowing us to run, jump, and throw objects. In order for these actions to occur, various muscle groups on both sides of the body must stretch and contract simultaneously in order to provide stability. Fascia, an often overlooked part of the human body, provides us with this elastic strength and stretch capacities, and the slings are strong examples of this. We explored two fascial subsystems in Part 1-the anterior and posterior oblique slings-that are extremely important for everyday activities and sports alike. But before we introduce two more in this article, it would only make sense if we were to take a couple of steps back and shed some light on some basic principles of the fascial system.

Fascia is a band of connective tissue beneath the skin that attaches to and encloses muscles. It is considered to be viscoelastic, which means that it has the ability to slide without friction, as well as return to its original shape after being stretched. This is important in the context of movement because this gives muscles the ability to transmit elastic stored energy without being impeded by friction. In addition, fascial fibers are heavily innervated with sensory nerve endings which give us the ability to understand where our bodies are in space, among other things.

When one refers to a fascial sling, they are speaking of an anatomical landmark where there is a high concentration of fascial tissues. Each sling has a set of particular functions, but overall, they play an integral role in global movement and control of transmitting forces from lower-to-upper and upper-to-lower extremities. In Part 1, we explored the structure and function of the anterior oblique sling, which is made up of one side’s external obliques and contralateral (opposite side) internal obliques and adductor complex. We also explored the posterior oblique system, which is made up of the latissimus dorsi muscle on one side and the gluteus maximus muscle on the other. In Part 2, we are going to introduce you to two more primary sling systems, which to athletes are extremely important for posture, basic motor control, and force expression.

The lateral sling consists of the lateral gluteus muscles (the gluteus medius and minimus) and adductor group on one side, as well as the opposite side’s quadratus lumborum muscle. This sling is responsible for frontal plane (think side-to-side) stability, along with the stability of the pelvo-femoral relationship during single-leg movements. For example, as a pitcher begins to push off the mound and stride towards home plate before he releases his pitch, the lateral sling allows for stability of the push-off leg and gives rise to powerful force being produced.

Last but not least in our exploration of fascial slings is the deep longitudinal sling. Composed of the erector spinae muscle group, it extends down through the same side’s thoracolumbar fascia, deep external rotator muscles of the gluteals, the iliotibial (IT) band, and peroneals. The sling subsystem is responsible for stabilizing the body from the ground up. It helps to provide force from the ground up through the foot and ankle, into the trunk, and back down to the ground. In order to picture this sling in action, imagine a basketball player going in for a breakaway dunk. As they take that last step before jumping off, force is transmitted through the ground and into that single leg, traveling upwards through the body via the deep longitudinal sling. As for everyone else that isn’t going in for thunderous dunks, the deep longitudinal sling can be seen as playing a dominant role in all other gait motions during everyday movement.   

Try out the following exercises and take advantage of everything that the deep longitudinal and lateral slings can provide for your goals!

The Body Bar 1-Leg Goodmorning is a fantastic exercise that targets the deep longitudinal sling. Incorporating the feet, lower leg muscles, glutes, lower back, and core, this movement is great for those looking to challenge their balance, as well as develop their single-leg stability and strength. In order to do this movement correctly:

• Position a Body Bar or light barbell behind your back on your upper trap muscles
• Transferring your weight onto a single leg, bow forward as you hinge at the waist
• Maintaining a neutral spine position, keep a straight line from your upper torso through to the leg that is not in contact with the ground as you extend the leg behind you
• Hinge and drive the non-supporting leg back until you begin to feel your lower back round over (or until your torso becomes parallel with the floor); pause in this position for one second
• Return to the starting position by extending your back and returning your foot to the ground while maintaining the neutral spine position

This exercise can be used as a part of a warm-up to incorporate some stability work or as a part of a pairing of exercises during the workout; aim for 2-4 sets of 8-10 single-leg hinges per side.

The KB Offset Elevated 1-Leg Squat with Knee RNT is a great single-leg variation that focuses on strengthening the adductor and lateral glute muscle on the stance leg, as well as the lateral core on the opposite side. In addition to strengthening the lateral sling, it is also a fantastic stability drill that can help to improve your movement efficiency and power. In order to perform this exercise correctly:

• Position a band to a sturdy frame and attach it above your knee as you stand on a 12” box
• Position the 12” box far enough away from the frame so that the slack of the band is pulled taut
• Holding a light to medium weight kettlebell on the non-stance side, position yourself on the edge of the box
• Maintaining a neutral spine, sit back and begin to descend into a single-leg squat, holding the kettlebell by your side, as you aim to tap the heel of the non-stance leg on the ground
• Pause on the ground in order to own the movement and maintain stability, before you ascend from the squat and back to the starting position

This exercise can also be used as a part of a warm-up in order to prime the core and leg muscles, or it can be used as a part of a pairing of exercises during the workout; aim for 2-4 sets of 5-8 single leg squats per side.

Lastly, the KB 1-Arm Front Rack Lateral Step-Up to Lateral Lunge is a combination exercise that targets the lateral sling by incorporating the inner groin muscles and lateral glute muscle on the leg that is performing the step-up, as well as the opposite side core and lower back that is resisting lateral side bending. This exercise is a fantastic total body exercise that will strengthen the lower body and core, as well as provide a new stimulus that will challenge your coordination and flexibility. In order to perform this exercise:

• Position a light to moderate weight kettlebell in the front rack position on one side, and stand on the side of a 12” box so that the kettlebell is on the opposite side of the box
• Laterally step up onto the box while maintaining a neutral spine and positioning the majority of the weight onto the stepping leg
• Return to the starting position by laterally stepping down off of the box, making sure to keep the pelvis neutral and not allowing the core to rotate or bend to the side
• After returning back to the ground, perform a lateral lunge to the side furthest from the box. Make sure to keep a proud chest and not allow yourself to round over, as well as maintain an alignment of the bent knee with your foot.
• Push off of the foot and return to the starting position before beginning the next rep

This exercise makes for a fantastic drill to warm up and potentiate the lower body and core for the subsequent workout, or it can be used as an exercise in and of itself within the session; aim for 2-4 sets of 5-8 repetitions per side.

The involvement of all four fascial slings during human movement is expansive. Therefore, training them should involve more than just the traditional exercises that stay within their own cardinal plane, such as front-to-back, left-to-right, and rotation along one axis. Human movement is much more sophisticated than that, and now that you understand the structure and function of the fascial sling subsystems, you can begin to incorporate more novel training ideas to reflect the dynamic nature of sport and activity. It’s not difficult to emphasize sling training; anything can be considered “sling-dominant” if you can learn how to incorporate the different musculature that comprises each of the slings. If one were to create parameters around this type of training, you should always consider:

• Training unilaterally with either a contralateral (opposite side) load to emphasize the anterior/posterior oblique slings or ipsilateral (same side) load to emphasize the deep longitudinal or lateral slings.
• Incorporating movements that are cross-body oriented and require the body to provide a high degree of internal stability.
• Picking exercises that include both an upper-body motion, as well as a lower-body motion in order to connect the two halves.